The hit reality singing contest "The Voice" is gearing up for its ninth season with mainstay coaches, Adam Levine and Blake Shelton confirmed to return. However, there has been no official announcement yet about the remaining two slots.

Aside from Levine and Shelton, Christina Aguilera has enjoyed the longest tenure as a judge for "The Voice" making her the most logical choice. The award-winning singer has never won in any of the seasons that she has coached, and has managed to go only as far as the second place in season five. Aguilera had also expressed her desire for another female coach to join her in the future. "I would love to see two females on the same season in the red chairs," the singer stated in a recent interview with Access Hollywood Live. "We need more female power because, look what I have to put up with all alone, all by myself."

However, a source close to the production for NBC has told Radar Online that staffers on the sets of the show are hoping that Aguilera does not return for the next season. "No one wants Christina to come back as a judge on season nine of The Voice," the source said. According to previous reports, the singer had angered the production staff by repeatedly being late and constantly arguing with the other coaches, particularly Adam Levine. "She was really difficult to work with this season. Tensions between her and Adam were consistent, but she also just had a really bad attitude."

Despite the previous season of "The Voice" seeing some great performances, the show's rating had dropped to an all-time low. An insider has revealed to Hollywood Life that the show's producers were looking at pop superstar Justin Bieber to join the panel of judges for season nine. "He wants to mix it up to get ratings up and get younger viewers to watch the show," the insider said. "The first thing the producers plan to do is change up the judging line-up and one of the seats the show wants to fill is with Justin Bieber." At 21-years-old, Bieber will become the youngest judge to (possibly) join the show.

There has been no word from season eight winning coach Pharrell Williams, but according to Hollywood Life, the showrunners are looking to pair the three guys, Levine, Shelton and Bieber, with a female coach, possibly with former coaches Gwen Steffani or Shakira.